1. Field of the Invention
The present invention relates generally to tubular lock mechanisms and, more specifically, to such lock mechanisms as which incorporates an adjustable backset. More particularly, the present invention discloses an improved backset assembly incorporating modified inner and outer casing parts, as well as a novel “T” shaped hook portion associated with a sandwichingly disposed actuating plate, for the purpose of providing improved backset adjustment.
2. Description of the Prior Art
The prior art is well documented with examples of tubular lock assemblies with some form of adjustable backset structure. In particular, a desirable feature of such assemblies is the ability to conform to both longer and shorter backsets.
A first example of a tubular lock with backset adjustability is set forth in U.S. Pat. No. 6,293,597, issued to Huang, and which teaches a latch bolt cylinder engaged with a casing consisting of two casing parts. An actuating plate is mounted between the casing parts and includes two separate teeth and protrusions. A follower plate, including two separate teeth, is in close contact with the actuating plate and to which the protrusions bear against. A spindle of the tubular lock bears against two teeth of the follower plate, thereby allowing the actuating plate to retract the latch bolt indirectly. Alternatively, the actuating plate can be directly actuated to retract the latch bolt.
Another example of the prior art is set forth in U.S. Pat. No. 6,257,630, issued to Huang, and which teaches a tubular lock including a latch bolt cylinder that may be extended beyond the doorplate or retracted there into. A casing consists of two casing parts and is engaged to an inner end of the latch bolt cylinder. An actuating plate is mounted between the casing parts and includes two teeth and a number of protrusions. A follower plate is removably held by the protrusions and also has two teeth. A spindle of the tubular lock bears against the teeth of the follower plate or the actuating plate, thereby allowing the actuating plate to retract the latch bolt directly or indirectly. A movable plate is mounted between the casing parts and may be extended beyond the casing parts. The movable plate includes a positioning hole through which one of two mounting posts of the tubular lock extends.
Finally, another version of a latch bolt mechanism is disclosed in U.S. Pat. No. 6,334,635, again issued to Huang, and which differs from Huang '630 in that it teaches the teeth associated with the actuating plate as including a block formed thereon, the blocks being pressed against by a follower plate that also includes two teeth. When either tooth of the actuating plate or follower plate is pressed against by a spindle of the lockset, the latch bolt is retracted. An extension casing is mounted around the plates and movable toward or away from the latch bolt housing. The extension casing includes a first hole and a second hole through which the spindle of the lockset is selectively extended.